Holographic and other microstructure or refractive images are applied to printed material to capture the visual attention of the viewer by producing elaborate visual effects via light refraction and reflection. Such applied imagery can produce different viewing effects depending on the viewing angle, light source, and image details. Additionally, since holographic and other microstructure imagery is difficult to manipulate, copy or reproduce, holograms and other microstructure or refractive images applied in a pre-determined registration with printing on a substrate are particularly useful for security purposes.
Conventional systems for creating holograms or other cast images in registration with printing on a substrate use, inter alia, drums and can produce problematic repeat lines in a resin layer in the final product corresponding to seams between adjacent relief image masters mounted on the drums. For example, electroformed metal masters may be welded together or plastic masters may be ultrasonically butt-welded, or a number of masters may be adhered to the surface of the drum with the impressing surfaces of the masters facing out. In each case seams are present which can be impressed onto the receiving substrate along with the intended imagery.
Current systems for applying holographic and other microstructure images using heating also have important drawbacks. For example, applying holograms to rigid resin substrates with a heated drum to form microstructure images in a hardened resin substrate can produce image distortion due to the substantial heat and pressure required to impress the image into the rigid substrate. Similarly, applying further heating to previously heat-impressed films, such as the heat necessary to apply shrink film webs with microstructure images to container surfaces, can distort the images, effectively causing them to disappear or to lose some of their holographic or other refractive properties.
Systems for impressing holographic and other microstructure or refractive images into a layer of curable liquid resin using drums with adjacent relief image masters (as described above) and then curing are also known. These systems suffer shortcomings in addition to those stemming from the seams between adjacent masters on the drum. For example, it is difficult to maintain accurate registration between the impressing image on the drum and printing on the substrate carrying the curable liquid resin. This problem is exacerbated when the system is run at high speed. Indeed, current systems for impressing holographic and other microstructure or refractive images into a layer of curable liquid resin using drums with adjacent relief image masters offer no means for fine tuning the alignment between the impressing image on the drum and printing on the substrate carrying the curable liquid resin.
Thus, systems for creating holographic and other microstructure or refractive images in registration with printing on a substrate, which optionally eliminate repeat lines, which reduce image distortion and which provide holographic images that stand up to subsequent heating would represent important contributions to the art. Furthermore, if such systems were made available that achieved highly accurate registration at high speed, that accommodated large images, or that eliminated the down time associated with constant re-application of the same drum-mounted impressing images particularly, significant contributions to the art would be at hand.